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    <title>Document</title>
</head>
<body>
    <script>
        let arr = [2,1,4,3,'a',4,5,3,4,1,6]
        let str = 'a'
        let s = new Set(arr);
        console.log(s.size);//length
        // s.clear()//清空
        // console.log(s);
        s.delete('a')//删除某一项
        s.add(7)//添加
        console.log(s.has(6));//是否包含6
        console.log(arr.includes(5,7));//从7开始检索有数组中有没有5
        console.log(str.repeat(20));//重复输出20次
        console.log(s);
    </script>
</body>
</html>